1. Field of the Invention
The present invention relates to a graft precursor comprising aromatic polycarbonate resin and vinylic copolymer containing a radically polymerizable organic peroxide group in the molecule, and a process for producing grafted aromatic polycarbonate resin from the graft precursor.
The grafted aromatic polycarbonate resin obtained according to the present process can produce injection moldings with much less optical distortion owing to its distinguished transparency and flowability and is widely applicable to optical uses such as optical disks and optical lenses and also provides useful compositions for a compatibilizer, an adhesive, a paint, a coating agent and a modifying agent.
2. Related Prior Art
So far, known materials for transparent moldings directed to optical purposes include acrylic resin having good transparency and flowability and a small double refraction (JP-A-56-131654, etc.). However, the acrylic resin has such disadvantages as a low heat resistance, for example, up to 70.degree. C., a low impact resistance and a high tendency for warping due to moisture.
To eliminate these disadvantages, it has been proposed to use polycarbonate resin having a viscosity average molecular weight of 15,000 to 18,000 as a molding material for disks, lenses, etc. (JP-A-58-180553), but the polycarbonate resin still has disadvantages such as insufficient flowability, etc., and thus has a limit to its applications.
In order to improve the flowability of aromatic polycarbonate resin, it has been proposed to melt-blend the aromatic polycarbonate resin with vinylic resin such as polystyrene, polymethylmethacrylate, AS resin, maleic anhydride-styrene copolymer, etc., but it is difficult to make dispersed particle sizes less than 1 .mu.m due to the non-compatibility, resulting in optical uneven blends. It has been also proposed to use a vinylic monomer as a solvent for the aromatic polycarbonate resin and subject the aromatic polycarbonate resin to a bulk graft polymerization (JP-A-63-196612), where the dispersed particle sizes can be made less than 0.2 .mu.m, but a large amount of washing solvent must be employed and post-treatments are complicated. It has been also proposed to conduct suspension graft polymerization (JP-A-62-138514), where the graft efficiency of the resulting resin compositions is smaller than that obtained by the bulk polymerization, and a high haze as an important property for optical materials is a problem.
A process for producing a graft precursor on the basis of a radically polymerizable organic peroxide is disclosed in JP-A-63-270713, JP-A-63-312305, JP-A-63-312306, JP-A-1-131220 and JP-A-1-138214, where the radically polymerizable organic peroxide is impregnated and polymerized in polypropylene or polyethylenic polymer. A method for utilizing the graft precursors as thermoplastic resin compositions is disclosed in JP-A-1-92252, JP-A-1-113449, JP-A-1-113456, JP-A-1-252660 and JP-A-1-256564, where the Tg of each the resins to be impregnated with vinyl monomer, radically polymerizable organic peroxide, etc. is so low, for example, -8.degree. C. for polypropylene and -125.degree. C. for polyethylene (Encyclopedia of Polymer Science and Engineering, Second Edition, Vol. 7, page 185), that a sufficiently high impregnation temperature than the Tg of the resin to be impregnated can be selected owing to use of an aqueous suspension, and the resin molecules are more active, resulting in satisfactory impregnation and good uniform polymerization.
However, in the case of resins having a Tg higher than 100.degree. C., such as aromatic polycarbonate resin, no impregnation temperature higher than 100.degree. C. can be used for the aqueous suspension, and thus it has never been so far contemplated to impregnate the aromatic polycarbonate resin with vinyl monomer, radically polymerizable organic peroxide and polymerization initiators to conduct graft polymerization.